1. Field of Invention
The present invention relates to an inverted-F antenna, and more particularly to a dual-band inverted-F antenna.
2. Related Art
Wireless communication technology employing electromagnetic waves to transmit signals does not need connecting wires for communicating with remote devices. Thereby, products applying the wireless communication technology are advantageous in portability, and thus the types thereof are increasingly growing, such as mobile phones and notebook computers. Further, as these products transmit signals through electromagnetic waves, an antenna for transmitting/receiving electromagnetic wave signals has become essential. Currently, an antenna is mainly exposed out of or built in a device. However, the antenna exposed out of a device not only affects the size and appearance of the product, but is also easily bent or fractured under the impact of an external force, so the built-in antenna has become a trend.
As for a current 3C device, in order to achieve multi-functions, a Wi-Fi antenna is further mounted in addition to a 3G wireless communication antenna. Along with the trend of developing smaller and more sophisticated 3C products, the space for disposing antennae is gradually reduced, and thus adjacent antennae may interfere with each other. As a result, the above situation may directly lead to a decrease of the radiation efficiency of the antennae and affect the signal quality.
FIG. 1 is a schematic view of a conventional inverted-F antenna. The inverted-F antenna has a striped radiation element 1, a sheet-like ground element 2 spaced from and facing the radiation element, and a conductive pin 3 and a signal feed-in portion 4 located between the radiation element 1 and the ground element 2. The conductive pin 3 connects one end of the radiation element 1 to the ground element 2 for functioning as a grounding pin. The signal feed-in portion 4 is disposed at a central position between two ends of the radiation element 1, for receiving signals fed in through a signal line 5. When the signal feed-in portion 4 receives a fed-in current from the signal line 5, the current is split to flow in the left and right directions. When the current directly flows toward the conductive pin 3 from the signal feed-in portion 4, as the current flows in opposite directions through the signal feed-in portion 4 and the conductive pin 3, the current on the left path is counteracted without causing any resonance to generate electromagnetic waves. The length of the right path is equivalent to that of the right side of the signal feed-in portion 4 in the radiation element 1, i.e., approximately a quarter wavelength. Therefore, electromagnetic waves at a specific frequency may be generated. Then, electromagnetic signals at the frequency are further induced, and the induced signals are transmitted to the signal line 5 through the signal feed-in portion 4 so as to be conducted out.
Thereby, the conventional inverted-F antenna can only transmit/receive mono-band signals, and fails to meet the multiplexing requirements. Meanwhile, if the inverted-F antenna is disposed adjacent to others, the radiation efficiency thereof may be affected.